1. Field of the Invention
The present invention relates to a flow cell for introducing a sample under high pressure into a measuring instrument, a method for manufacturing the flow cell, and a particle measuring instrument using the flow cell.
2. Description of the Prior Art
A high pressure fluid is used in a material gas used in a production process for an electronic device, compressor air for a machine driven jet gun and the like. A liquid phase, a gaseous phase, and a super critical phase exist in the high pressure fluid. In particular, in the case of the high pressure fluid used in the production process for the electronic device such as a semiconductor, it is required to control small particles contained in the fluid. Under the present circumstances, it is possible to measure the particles up to a pressure of 0.7 MPa using a fine particle measuring instrument which is available in the marketplace. In the case of high pressure gas, the gas is measured by reducing the pressure to 0.7 MPa using a regulator. When the measured particle diameter is large, the particles can be controlled by the compressor air and the like, but, in this case, the pressure is reduced to atmospheric pressure for measurement. Since a sample cannot be measured under a high pressure condition even by a densitometer and a chemical composition analyzer, the pressure must be reduced for measurement.
A flow cell used in a conventional particle measuring instrument is shown in FIG. 7. A flow cell 105 of a rectangle shape is known, of which the flow channel 104 is formed by combining four optically transparent rectangular flat plates 100 through 103 by welding (e.g., Patent Document 1).
Patent Document 1: Japanese Patent No. 3530078
In the conventional particle measuring instrument, there is another means for measuring the particles in a liquid or a reactive gas in a floating condition using a flow cell such as quartz or sapphire. However, a limit of the sample pressure which is in practical use is 0.7 MPa due to withstand pressure limitations and the flow cell.
As one means for measuring particles floating in the high pressure gas (air/inert gas) of up to 1 MPa, there is a method for introducing a sample into a high pressure chamber (particle detecting area) through a nozzle without using the flow cell. However, this method cannot be applied in principle to the measurement of particles under a liquid phase, a reactive gas phase or a super critical phase because the sample mixes with an existing media (normally, air) within the chamber. Further, a mechanism with a nozzle may be complicated and it is also difficult to obtain withstand pressure performance above 1 MPa.
Referring to the method for measuring the particles by reducing the pressure using the regulator, disturbance such as dusting by the regulator is caused. Referring further to the liquid phase or super critical phase, if the pressure is reduced, since such a phase may not be maintained, it is necessary to measure the particles while maintaining the pressure.